Piezoelectric crystal



June 5, 1945. B. TENENBAUM I PIEZOELECTRIC CRYSTAL Filed March 28, 1944 Izq/v err/tor l3- Tenezzba/um 277% .15@ 2 i PatentedJune' 5,/ 1945A jUNlTEo sTATEs Y A PATENT oFEicE PIEZELEl7`;:;7CRYS1;AL

Berko Tenenbaum, London, England application March u, 1944, serial No. 52ans In Great Britain November 11, 1942 `s claims. (ci. 1v1-321) The present invention consists in a. mounting of y piezo-electric crystal in which the distance between the surface of the crystal and the electrode facing it is varied by a straight line sliding movement between the two members respectively carrying the crystal and ,the electrode facing it, the said straight line forming a small angle with the opposing parallel surfaces of the crystal and of the electrode facing it.

In the accompanying drawing which illustrates, `by way of example, two methods of carrying tlfe invention into effect, Figures 1 and 2 show diagrammatically the principles of these two methods, whilst Figures 3 vand 4 show respectively in sectional elevation and side view, partly in secton, one embodiment of the invention according to the second method.

Referring to Figure 1 illustrating the first method, two wedge-shaped supporting frames fifa of insulating material are arranged in opposition to each other in such a manner that their opposing surfaces are parallel to each other, and one of them fz is adapted to slide relatively to the other one f1, in a direction m at a small angle a with respect to their opposing parallel surfaces.

On the latter surfaces, the wedge-shaped member f1 carries the electrode e1 and thereon the crystal c, whilst the sliding wedge-shaped member l: carries the electrode ez the facing surfaces of the latterand of the crystal being and remaining parallel to each other when they are approaching or are being removed from each other during the relative sliding movement. y

Referring to Figure 2 illustrating the second method, the two wedge-shaped frames fifzare arrangedy with their parallel opposing surfaces in contact with each other and one of them l: is adapted to slide along the-other f1 in the direction x, always remaining in' contact with it. As in the arrangement according o Figure i. the supporting frame l1 carries the electrode ei and crystal c. and the supporting frame fa the electrode ez, but in this case the opposing surfaces of the electrode en and crystal c are nc longe;` parailel to the inclined surfaces of the wedgeshaped supporting frames but only parallel to However, as in the arrangement each other. according to the first method, the variation of the distance a between the parallel surfaces lof electrode e: and crystal cis dependent` upon the small angle a, which the direction of displacement of the wedge-shaped member fz, viz., its inclined sliding surface, forms with the said parallel sur faces.

For the sake of clear-ness the angle a is shown exaggerated in the drawing. In'reality, it is less than 10.

By the use of either of the arrangements above referred to it is possible to effect and stabilise an air gap variation up to 'about 9600 cf a micron, corresponding to a frequency variation of about I:t'soooooo Referring to Figures 3 and 4 illustrating, byy way of example, one practical form for carrying the invention into effect according to the second arrangement above referred to, b is a housing of aluminium secured by screws d to the wall g of the apparatus in which the crystal-is' incorporated;

n is a, brass bushing in which the spindle i is mounted in screw-threaded engagement in order to be displaced axially when operated by the` k is a dial and lil: are two abutments secu to the brass bushing h and the spindle i :espectively, to limit vthe extent of rotationA of tle spindle and thereby its axial displacement.

'Ihe stationary wedge-shaped frame f1 is secured to a separate aluminium plate e1 to which the quartz plate c is attached and which forms the .one electrodev the latter forming part of the and presses against the electrode e: xed in the frame fz. the latter is constantly kept in sliding contact with the frame f1.

In order` to obtain a gradual variation of frequency without air-gap resonance use is preferably made of a Y-cut crystal; .alternatively the device may be evacuated or be filled with a gas, for instance hydrogen.

-The details for carrying the invention into efrect may be modined'without departing from the scope of the invention.

I claim:

l. A piezc-electric crystal mounting comprising a piezo-electric crystal, an electrode in contact with the said crystal, a member carrying the said crystal and electrode, a second electrode arranged at a distance from the said crystal so that small angle with the opposing parallel surfaces of the crystal and the electrode facing it, whereby the distance between the said parallel surfaces is varied.

2. A piezo-electric crystal mounting as claimed in claim 1, in which the two carrying members are wedge-shaped frames of insulating material arranged in opposition to each other, the opposing parallel surfaces of the crystal and electrode being parallel to the inclined surfaces of the werke-shaped frames.

3. A piezo-electric crystal mounting as claimed in claim l, in which the two carrying members are wedge-shaped frames of insulating material arranged in opposition to and in sliding contact with each other, the opposing parallel surfaces of the crystal and electrode forming a small angle with the sliding contactsurfaces of' the wedgeshaped frames.

BERKO TENENBAUM. 

